title: Crystal structure of Schmallenberg orthobunyavirus nucleoprotein-RNA complex reveals a novel RNA sequestration mechanism.
abstract: Schmallenberg virus (SBV) is a newly emerged orthobunyavirus (family Bunyaviridae) that has caused severe disease in the offspring of farm animals across Europe. Like all orthobunyaviruses, SBV contains a tripartite negative-sense RNA genome that is encapsidated by the viral nucleocapsid (N) protein in the form of a ribonucleoprotein complex (RNP). We recently reported the three-dimensional structure of SBV N that revealed a novel fold. Here we report the crystal structure of the SBV N protein in complex with a 42-nt-long RNA to 2.16 Å resolution. The complex comprises a tetramer of N that encapsidates the RNA as a cross-shape inside the protein ring structure, with each protomer bound to 11 ribonucleotides. Eight bases are bound in the positively charged cleft between the N- and C-terminal domains of N, and three bases are shielded by the extended N-terminal arm. SBV N appears to sequester RNA using a different mechanism compared with the nucleoproteins of other negative-sense RNA viruses. Furthermore, the structure suggests that RNA binding results in conformational changes of some residues in the RNA-binding cleft and the N- and C-terminal arms. Our results provide new insights into the novel mechanism of RNA encapsidation by orthobunyaviruses.
authors.affiliation: Biomedical Research Centre, Norwich Medical School, University of East Anglia, Norwich Research Park NR4 7TJ, United Kingdom.
authors.forename: Haohao
authors.initials: H
authors.lastname: Dong
authors.forename: Ping
authors.initials: P
authors.lastname: Li
authors.forename: Bettina
authors.initials: B
authors.lastname: Böttcher
authors.forename: Richard M
authors.initials: RM
authors.lastname: Elliott
authors.forename: Changjiang
authors.initials: C
authors.lastname: Dong
mesh_terms: D000818:Animals; D001665:Binding Sites; D018360:Crystallography, X-Ray; D046911:Macromolecular Substances / Q000737:chemistry / Q000648:ultrastructure; D008854:Microscopy, Electron; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D019590:Nucleocapsid Proteins / Q000737:chemistry* / Q000648:ultrastructure; D016851:Orthobunyavirus / Q000737:chemistry* / Q000472:pathogenicity / Q000648:ultrastructure; D020836:Protein Structure, Quaternary; D012367:RNA, Viral / Q000737:chemistry*; D055672:Static Electricity
chemical_list: D046911:Macromolecular Substances; D019590:Nucleocapsid Proteins; D012367:RNA, Viral
keywords: RNA replication and transcription; Schmallenberg virus; bunyavirus; nucleoprotein structure; orthobunyavirus